Need Spam Karma help

I have a heavily used blog and we have someone who is personally spamming the blog with a very angry message. It’s not a bot, just a person. We have tried putting strings from the message (he keeps copying and pasting the same thing) into the regex content blacklist. I gave it a score of -100 but anytime i put those strings in a comment, it still comes through. When i put the string in, i put it in with / / on either side the words because I think this is the way you add it. Anytime i a make a comment with the string in it, the blacklist shows that that string just went through but doesn’t block it. The person keeps changing their ip address so an ip block won’t do either. I have put almost all of the spam karma settings on supastrong and have even set severity to total beeatch. Am I putting the string into the blacklist properly? Any help on with this would be greatly appreciated.